Multi-mode landmine detector

ABSTRACT

An multi-mode target detection system includes a ground penetrating metal detector and a ground penetrating radar detector permitting operation of the system in a variety of target detection modes. The system includes a control section having a selection device for selecting at least two operating modes from the group consisting of a buried land mine detection mode, a through wall detection mode, a perimeter warning mode, a buried cache detection mode and an in-wall cache detection mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of and claimspriority to U.S. application Ser. No. 10/918,736, filed on Aug. 16,2004, which claimed priority to U.S. Provisional Application No.60/495,871 filed on Aug. 19, 2003 and U.S. Provisional Application No.60/495,084 filed on Aug. 15, 2003, all of which are incorporated byreference. This application also claims priority to U.S. ProvisionalApplication No. 60/591,617 filed on Jul. 28, 2004, which also isincorporated by reference.

TECHNICAL FIELD

This document relates to the detection of buried landmines and othertargets.

BACKGROUND

Landmines are area denial weapons and are intended to slow, re-direct orobstruct the mobility of military forces. The landmine threat usuallycontinues long after the conflict ends, posing great risk to thecivilian population. Since World War II, handheld landmine detection hasbeen based on the metal detector. Unlike older metal-cased landmines,today's modern anti-tank and anti-personnel mines are made primarily ofplastic and have very little metal content. Landmines by their verynature are laid in areas of conflict, and the surrounding soil typicallycontains high levels of metal clutter, e.g., shrapnel and metal shellcasings. This clutter significantly increases the difficulty of findingmodern mines using only a metal detector.

SUMMARY

In one general aspect a multi-mode mine detection system includes aground penetrating metal detector, a ground penetrating radar detectorand a control section having a selection device for selecting at leasttwo operating modes from the group consisting of a buried land minedetection mode, a through wall detection mode, a perimeter warning mode,a buried cache detection mode and an in-wall cache detection mode.

Implementations may include one or more of the following features. Forexample, the ground penetrating metal detector may include atransmitter, a coil coupled to the transmitter to produce a magneticfield, and a signal processor coupled to the coil and configured todetect a secondary magnetic field.

The ground penetrating radar detector may include a radio frequencygenerator. The radio frequency transmitter may be coupled to the radiofrequency generator to transmit radio-wave signals toward the ground.

The ground penetrating radio detector may include a radio frequencyreceiver that receives radio-wave signals from the ground, and a signalprocessor coupled to the radio frequency receiver to detect theradio-wave signals, wherein the radio frequency receiver includes anantenna.

The operating modes supported by the control section may include one ormore, or all of the buried land mine detection mode, the through walldetection mode, the perimeter warning mode, the buried cache detectionmode and the in-wall cache detection modes.

The metal detector may include a coil that produces a magnetic field andthe radar detector may include a transmitting antenna that transmitsradio-wave signals toward the ground and a receiving antenna thatreceives radio-wave signals reflected from objects within the ground.The antennas may be surrounded by the coil and the antennas may beshielded from external electromagnetic radiation.

An output device may be provided that outputs a signal indicating apresence of an object if either the ground penetrating metal detector,the ground penetrating radar detector, or both detect the presence ofthe object.

The ground penetrating radar detector and the ground penetrating metaldetector may be housed in a single housing. The operation of the metaldetector may not interfere with operation of the radar detector.

The system may include an output device for indicating a detection of atarget in the at least two operating modes. The output device mayincludes a visual display, an audio alarm and/or a visual alarm.

In another general aspect, a target detection system may include anintegrated search device housing a radio-wave transmitter and a metaldetector coil. The system may include a first set of electroniccomponents coupled to the radio transmitter. The system may include asecond set of electronic components coupled to the metal detector coil.The system may include a processor for detecting a target through atleast two modes that may be selected from the group consisting of aburied land mine detection mode, a through wall detection mode, aperimeter warning mode, a buried cache detection mode and an in-wallcache detection mode.

Implementations may include one or more of the following features. Thesystem may include a radio-wave receiver, wherein the radio-wavetransmitter and receiver may be shielded from external electromagneticradiation. The operating modes supported by the control section mayinclude all of the buried land mine detection mode, the through walldetection mode, the perimeter warning mode, the buried cache detectionmode and the in-wall cache detection mode.

The system may include an output device for indicating a detection of atarget in the at least two operating modes. The output device mayincludes a visual display, an audio alarm and/or a visual alarm.

In another general aspect, a method of detecting targets in a multi-modetarget detection system may include selecting an operating mode fordetecting a target, wherein the operating mode may be selected from thegroup consisting of a buried land mine detection mode, a through walldetection mode, a perimeter warning mode, a buried cache detection modeand an in-wall cache detection mode. The method may include transmittingradio-wave frequency energy into a surrounding region. The method mayinclude detecting radio-wave frequency energy reflected by an object inthe surrounding region. The method may include analyzing data obtainedfrom transmitting and detecting radio-wave frequency to detect thetarget in the selected operating mode.

Implementations may include one or more of the following features.Selecting the operating mode may include initiating a predetermined dataprocessing step for the selected operating mode.

In another general aspect, a method of detecting targets may includeproviding a detection system having a metal detector and a radardetector for collecting and analyzing data taken from a surroundingregion. The method may include selecting an operating mode for detectinga target, wherein the operating mode may be selected from the groupconsisting of a buried land mine detection mode, a through walldetection mode, a perimeter warning mode, a buried cache detection modeand an in-wall cache detection mode. The method may include detectingthe target with the detection system.

Implementations may include one or more of the following features.Detecting the target with the detection system may include analyzingdata taken from the surrounding region using the metal detector, andanalyzing data taken from the surrounding region using the radardetector.

The method may include training the detection system using a principalcomponents analysis of the background clutter data. Detecting the targetwith the detection system may include Doppler processing of data fromthe radar detector. The Doppler processing of data from the radardetector may be performed during the through wall detection mode and theperimeter warning mode. Detecting the target with the detection systemduring the through wall detection mode may further include analyzingdata taken from the surrounding region using the metal detector.

The method may include automatically adapting the detection system tothe surrounding region to determine whether a mine is present in thesurrounding region. Adapting the detection system includes using aprincipal components analysis of the data taken from the surroundingregion.

The method may include analyzing data taken from the surrounding regionusing a metal detector. The method may include analyzing data taken fromthe surrounding region using a radar detector based on the training. Themethod may include analyzing a depth of an object detected by the radardetector using the data. Analyzing the depth of the object may includetransforming data from the radar detector from the frequency domain tothe time domain. Analyzing the depth includes receiving data from two ormore antennas of the radar detector. Analyzing data taken from thesurrounding region using the radar detector may include using aprincipal component analysis of the data.

Aspects of the techniques and systems can include one or more of thefollowing advantages. The mine detection system uses both a radardetector and a metal detector to improve detection for mines and reducethe false alarm rate. Metal debris can mask the detection of mines.Because of this, a metal detector alone might not detect the presence ofa mine among metal debris. Additionally, a metal detector alone mightfalsely issue an alarm over metal debris even in the absence of a minebecause the metal detector cannot always distinguish metal debris frommines. Accordingly, the mine detection system, which uses a radardetector in addition to a metal detector, is able to reject metallicbattlefield debris that otherwise creates a significant signal.

Because clutter data (data from features other than mines) is the onlydata used to train the model of radar detector response to currentground conditions, the training and adaptation of the radar detectormodel is easier to perform than the training an adaptation of thosemodels requiring both clutter and mine data for training. Adaptation ofthe model to new environments is done automatically and on the fly,which reduces human resources and costs of training associated withoperation of the mine detection system. Collection of clutter data iseasier to implement than collection of mine data, which requirescollection of mine data for every site before use of the system.

Other features and advantages will be apparent from the description, thedrawings, and the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a mine detection system.

FIG. 2 is a block diagram of the mine detection system of FIG. 1.

FIG. 3 is a side view of the mine detection system of FIG. 1 partiallyopened from storage.

FIG. 4 is a side view of the mine detection system of FIG. 1 ready forstorage.

FIGS. 5 and 6 are, respectively, front and side perspective views of aninterface controller of the mine detection system of FIG. 1.

FIG. 7 is a perspective view of a battery pack of the mine detectionsystem of FIG. 1.

FIG. 8 is an exploded perspective view of the battery pack of FIG. 7.

FIG. 9 is a perspective view of an earpiece of the mine detection systemof FIG. 1.

FIG. 10 shows back and front perspective views of an electronics unit ofthe mine detection system of FIG. 1.

FIG. 11 is an exploded perspective view of a search device of the minedetection system of FIG. 1.

FIG. 12 is a perspective view of the search device of the mine detectionsystem of FIG. 1 without its lid to show internal components.

FIG. 13 is a block diagram of the metal detector of the mine detectionsystem of FIG. 1.

FIG. 14 is a block diagram of the radar detector of the mine detectionsystem of FIG. 1.

FIG. 15 is a perspecitve view of a kit for storing and transporting themine detection system of FIG. 1.

FIG. 16 is a flow chart of a procedure performed by a user forunpacking, preparing, and operating the mine detection system of FIG. 1.

FIG. 17 is a flow chart of a procedure performed by a user for preparingthe mine detection system of FIG. 1 for operation.

FIG. 18 is a procedure performed by the metal detector of the minedetection system of FIG. 1 for detecting a presence of a mine.

FIG. 19 is a flow chart of a procedure performed by the radar detectorof the mine detection system of FIG. 1 for detecting a presence of amine.

FIGS. 20 and 21 are side views of the search device of the minedetection system of FIG. 1.

FIG. 22 is a flow chart of a procedure performed by a user of the minedetection system of FIG. 1 after receiving an alert signal.

FIG. 23A shows an overhead view of a sweep pattern performed by a userof the metal detector of the mine detection system of FIG. 1.

FIG. 23B is a flow chart of a procedure performed by the user during thesweep pattern of FIG. 23A.

FIGS. 24A and 24C show overhead views of sweep patterns performed by auser of the radar detector of the mine detection system of FIG. 1.

FIG. 24B is a flow chart of a procedure performed by the user during thesweep pattern of FIGS. 24A and C.

FIGS. 25A and 25B show another implementation of the mine detectionsystem of FIG. 1.

FIGS. 26-28 are flow charts of procedures performed by a processor ofthe radar detector within the mine detection system of FIG. 1.

FIG. 29 is a graph of sample results produced by the processor using theprocedures of FIGS. 26-28.

FIG. 30 is a flow chart of an alternative processing procedure that maybe performed by the processor of the radar detector within the minedetection system of FIG. 1.

FIG. 31 is a representative view of a display during a through walldetection mode that utilizes Doppler ATR processing when a search deviceis flush against a wall.

FIG. 32 is a representative view of a display during a through walldetection mode that utilizes Doppler ATR processing when a search deviceis positioned away from a wall.

FIG. 33 is a schematic view showing a selection device for a minedetection system having a plurality of operating modes.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIGS. 1, 2, 13, and 14, an integrated mine detection system100 incorporates a metal detector 1350 (FIG. 13) and a radar detector1450 (FIG. 14) into a single integrated system for detecting mines,including those mines that would otherwise not be detected solely withthe use of a metal detector. The mine detection system 100 includes asearch device 105, an interface controller 110, and an electronics unit115. The search device 105 connects to the electronics unit 115 througha bundled set of wires 106 and the interface controller 110 connects tothe electronics unit 115 through a bundled set of wires 111. To ensurethat internal electronics are kept dry and secure, the bundled sets 106and 111 enter the search device 105 and the electronics unit 115 throughweatherproof seals 116. In general, the metal detector 1350 and theradar detector 1450 each include a set of electronics within the unit115 and transmitting and receiving components within the search device105, as further described below.

The mine detection system 100 includes an elongated shaft 120 coupled tothe search device 105, and an armrest 125 coupled to the shaft 120 witha cradle 127. The interface controller 110 is attached to the shaft 120to enable a user to access the interface controller 110 with a first armwhile resting her second arm in the armrest 125.

The mine detection system 100 also includes one or more audio outputdevices, such as an earpiece 135 that is coupled to the electronics unit115 and a speaker 137 (shown in FIG. 2) within the electronics unit 115.A power source such as a battery pack 140 is coupled to the electronicsunit 115 to provide power to the unit 115.

FIGS. 3 and 4 show the mine detection system 100 without the batterypack 140 and the earpiece 135. The shaft 120 is telescoping and is madeof segments 200 that slide into each other to adjust the length of theshaft 120 to accommodate the particular height of the user and toaccommodate compact storage (as detailed below). Each of the segments200 is secured in place relative to the adjacent segments 200 with a setof clamps 205 positioned between each pair of adjacent segments 200.Upon loosening a clamp, the smaller segment 200 can be slid into theadjacent larger segment 200, as shown in FIG. 3.

The shaft 120 is able to be folded relative to the cradle 127 at a joint210. The shaft 120 includes a latching yoke 212 that secures the shaft120 to the cradle 127 with a friction fit when the shaft 120 is foldedrelative to the cradle 127. The shaft 120 is secured in the open(unfolded) position relative to the cradle 127 by use of a latch 215 atthe joint 210.

Referring also to FIGS. 5 and 6, the interface controller 110 includes acontrol section 400, a pair of clamps 405, and a handle 410 extendingfrom the control section 400. The clamps 405 are sized to receive thecradle 127 with a friction fit to secure the controller 110 to thecradle 127. The interface controller 110 includes a housing 112 thathouses all of its internal components and provides the control section400, the clamps 405, and the handle 410. The housing 112 of thecontroller 110 can be made of any suitably durable material, such as,for example, molded plastic.

The control section 400 includes a set of switches that enable a user tocontrol operation of the mine detection system 100. The set of switchesincludes a power switch 415, a metal detection control switch 420, aradar sensitivity switch 425, an audio control switch 430, and a triggerswitch 435. The control section 400 also includes a set of indicatorsthat provide feedback to a user of the mine detection system 100. Theset of indicators includes a ready indicator 440 and a power andfunction indicator 445.

Referring also to FIGS. 7 and 8, the battery pack 140 is connected tothe electronics unit 115 with a cable 600 and a connector 605 (such as acircular twist lock connector) that mates with a connector 900 (shown inFIGS. 2 and 10) on the electronics unit 115. The battery pack 140includes a pair of clips 610 that can be used to attach the battery pack140 to a belt on a user. The battery pack 140 houses a battery 615within a case 620 having latches 625 and a lid 630 having a lip 635. Thecase 620 and the lid 630 mate with each other and are secured to eachother when the latches 625 lock to the lip 635. The case 620 and the lid630 can be made of any non-metallic durable material, such as, forexample, molded plastic. The battery 615 includes a connector 640 thatmates with a connector 645 of the case 620 when the battery 615 ishoused within the case 620.

Referring also to FIG. 9, the earpiece 135 includes a cable 800 and aconnector 805 (such as a circular twist lock connector) that mates witha connector 910 (shown in FIGS. 2 and 10) on the electronics unit 115.

Referring again to FIG. 2 and also to FIG. 10, the electronics unit 115includes a housing 136, a speaker 137 (FIG. 2) within the housing 136, aset of switches external to the housing 136 that enable a user tocontrol the unit 115, and a set of connectors 900 and 910 on the surfaceof the housing 136 that couple, respectively, to the connector 605 ofthe battery pack and the connector 805 of the earpiece 135. The set ofswitches includes a volume control switch 915. The internal speaker 137is positioned adjacent one or more openings 920 on a housing 136 topermit audio waves to emanate from the unit 115. The housing 136 can bemade of any suitable material, such as, for example, molded plastic.

The housing 136 houses a processor card 220, an interface card 225,electronics 230 of the metal detector, electronics 235 of the radardetector, and a power supply 240.

The power supply 240 is connected to the battery pack 140 throughconnectors 900 and 605, to the earpiece 135 through connectors 910 and805, to the interface card 225, and to the radar detector electronics235. The power supply 240 also connects to the interface controller 110to enable a user to turn the mine detection system 100 using the powerswitch 415. The processor card 220 is connected to the interface card225 and the metal detector electronics 230. The metal detectorelectronics 230 and the radar detector electronics 235 are controlled bysoftware that is run by their respective processors and that is storedwithin memory. The software may be modified to support a variety ofdetection modes and data analysis processes, and to permit improvementsto the functionality of the respective electronics 230, 235. The memorycan be either internal to the unit 115 or external to the unit 115, suchas, for example, through a portable storage device 245 that can beaccessed by the electronics 230 and 235 of the unit 115. Both the metaldetector electronics 230 and the radar detector electronics 235 areconnected to the search device 105, as discussed further below.

Referring again to FIG. 2 and also to FIGS. 11 and 12, the search device105 includes a lid 250 that mates with and connects to a base 255 toform a hollow enclosure. The lid 250 includes an extension piece 260 towhich the last segment 200 of the shaft 120 connects. The lid 250 andthe base 255 may be formed of any non-magnetic material, such as, forexample, molded plastic.

The hollow enclosure of the search device 105 houses the transmittingand receiving components of the metal detector and the radar detector.Thus, the hollow enclosure houses a magnetic field producing device suchas a coil 265 that acts as a transmitting/receiving component for themetal detector. Additionally, the hollow enclosure houses a radio wavetransmitter such as a transmitting antenna 270, and a radio wavereceiver such as a set of receiving antennas 275 and 280. The antenna270 acts as a transmitting component for the radar detector and theantennas 275 and 280 act as receiving components for the radar detector.

The components of the metal detector and the radar detector within thesearch device 105 are placed and designed so that operation of onedetector does not interfere with the results of the other detector. Forexample, each of the antennas 270, 275, and 280 can be shielded fromexternal electromagnetic radiation and such that they radiateradio-waves into a narrow path and receive only that electromagneticradiation from a downward direction that is approximately perpendicularto a bottom surface of the search device 105.

Referring to FIG. 13, the metal detector electronics 230 includes aprocessor 231 that is connected to the coil 265, a pulse generator 232coupled to the processor 231, and a transmitter 233 that receiveselectric signals from the pulse generator 232 and transmits the electricsignals in the form of an electric current to the coil 265. Theprocessor 231 is also coupled to one or more audio output devices 135,137 through the interface card 225 (FIG. 2). Referring to FIG. 14, theradar detector electronics 235 includes a processor 236 coupled to thereceiving antennas 275 and 280 and a radio frequency generator 237coupled to the processor 236 and to the transmitting antenna 270. Theprocessor 236 is also coupled to audio output devices 135 and 137through the interface card 225 or directly (FIG. 2).

Referring also to FIG. 15, the integrated mine detection system 100 istypically stored and transported in the form of a kit 1500 that includesthe system 100, the battery pack 140, and the earpiece 135. The kit 1500also includes a set of spare batteries 1505, a test piece 1510 thatmimics a mine and is used to test the system 100, and a set of trainingmaterials that are stored on an external memory device such as a floppydisk 1515 (as shown), a USB memory key, or a CD-ROM. The kit 1500 mayinclude a support sling 1517 that attaches to the interface controller110 and to clothing worn by a user, such as, for example, a load-bearingvest, to relieve some of the weight of the system 100 during operation.

The kit 1500 includes a storage and transport container 1520, anadditional support handle 1525 for carrying the container 1520, and abackpack 1530. The container 1520 is sized to receive the backpack 1530and includes a lid 1522 and a base 1524. The container 1520 may be linedwith cushioning such as foam 1535 to protect the system 100 duringstorage and transport. Additionally, the container 1520 may be vacuum orair sealed to prevent moisture from entering the system 100 duringstorage. The seal of the container 1520 is broken by use of an airpressure release valve 1540 on a front of the container 1520.

The backpack 1530 is sized to receive the system 100 in a folded state(shown in FIG. 4), the batteries 1505, the test piece 1510, the floppydisk 1515, and the support sling 1517 (if provided). Thus, duringstorage in the container 1520, all of the equipment is stored within thebackpack 1530, which is then stored in the container 1520. Such aconfiguration reduces size requirements for storage and transport.

Referring to FIG. 16, a procedure 1600 is performed to use the system100. Initially, the user unpacks the system 100 from the container 1520(step 1605) and assembles the system 100 prior to use (step 1610).Initially, during unpacking (step 1605), the user opens the valve 1540and unlatches the container lid 1522 from the base 1524. Then, the userremoves the backpack 1530 from the container 1520 and opens the backpack1530. The user then removes the system 100 and any other neededequipment from the backpack 1530.

Referring also to FIG. 4, during assembly (step 1610), the userunlatches the yoke 212 from the cradle 127 and unfolds the shaft 120away from the cradle 127. The user secures the shaft 120 with the latch215 and unfolds the electronics unit from the cradle 127, as shown inFIG. 3. The user rotates the search device 105 relative to the shaft 120and the interface controller 110 relative to the cradle 127, as shown inFIG. 1. The user also opens the clamps 205 and expands the segments 200out to a comfortable position. When the comfortable position is reached,the user closes the clamps 205 to secure the segments 200 and the shaft120 for use.

Referring also to FIG. 8, the user opens the latches 625, removes thebattery pack lid 630 from the case 620, and inserts the battery 615 intothe case 620 making sure the battery connector 640 is properly connectedto the case connector 645. The user replaces the lid 630 and closes thelatches 625. Then, the user connects the battery connector 605 to theelectronics unit connector 900, as shown in FIG. 10. If the earpiece 135is to be used along with the speaker 137, then the user connects theearpiece connector 805 to the electronics unit connecter 910, as shownin FIG. 10. Next, the user inserts her arm through the armrest 125 andgrabs the handle 410 of the interface controller 110 (FIGS. 1, 5, and6). The user can adjust the position of the handle 410 by rotating thehandle 410 and by sliding the handle and the controller 110 along thecradle 127. The user can also adjust the tightness of the armrest 125 toher personal comfort.

Once the system is unpacked and assembled (steps 1605 and 1610), theuser makes initial adjustments to the system 100 (step 1615). If onlythe earpiece 135 is to be used during operation (that is, the speaker137 is not active), then the user should connect the earpiece 135 to theunit 115 during these initial adjustments (step 1615) and prior tostartup. If only the speaker 137 is to be used during operation (thatis, the earpiece 135 is not active), then the user should not connectthe earpiece 135 to the unit 115 during these initial adjustments (step1615) and prior to startup. If both the earpiece 135 and the speaker 137are to be used, the user should connect the earpiece 135 after thesystem 100 is turned on (as discussed below).

After the initial adjustments are made (step 1615), the user starts thesystem 100 (step 1620). Initially, referring also to FIG. 5, the usersets the radar sensitivity switch 425 to a center position and pushesthe power switch 415 momentarily to the on position (for example, to theright). The user then lets the system 100 warm up for a predeterminedtime such as five minutes. Next, the user pushes the power switch 415momentarily to the off position (for example, to the left) to shut downthe system 100. Then, the user pushes the power switch 415 momentarilyto the on position once again while the search device 105 is resting onthe ground. The user then waits until the processor 231 or the processor236 sends a signal to the audio device 135 or 137 indicating that thesystem 100 is ready to be trained. The power and function indicator 445emits a signal (such as a flashing light) after the system 100 hascompleted startup (step 1620).

After startup (step 1620), the user prepares the system 100 (step 1625)by calibrating the system 100 to the local ground and electromagneticinterference (EMI) conditions and training the system 100, as discussedin detail below with respect to FIG. 17. Once the system 100 is prepared(step 1625), the user can then operate the system (step 1630), asdiscussed in detail below. When the user is finished operating thesystem 100 (step 1630), the user shuts down the system 100 by pushingthe power switch 415 to the off position (step 1635). After the system100 is shut down (step 1635), the user disassembles the system 100 (step1640) and repacks the system 100 (step 1645) in the backpack 1530 andthe container 1520 in a reverse order from which the system is assembledand unpacked.

Referring to FIG. 17, the user performs a procedure 1625 to prepare thesystem 100. Initially, the user performs a procedure for canceling theeffects of EMI conditions on operation of the metal detector (step1700). During this procedure, the user holds the search device 105 onthe ground but not above metal for a predetermined duration (such as 55seconds). During this duration, the user pushes the metal detectioncontrol switch 420 to the left momentarily, and the processor 231 causesthe audio device 135 or 137 to continually emit an audio signal such as“noise cancel” indicating to the user that the system 100 is beingcalibrated to the effects of the EMI conditions. At the end of theduration, the processor 231 causes the audio device 135 or 137 to emitan audio signal such as “noise cancel complete” indicating to the userthat the system 100 has been calibrated to the effects of the EMIconditions.

Next, the user performs a procedure for canceling the effects ofminerals in the soil on operation of the metal detector (step 1705).Before beginning this procedure, the user ensures that the area is freeof all metallic targets. The user then holds the search device 105 apredetermined height (for example, 6-10 inches) above the surface of theground and pushes and holds the metal detection control switch 420 tothe right (FIG. 5). At this time, the processor 231 causes the audiodevice 135 or 137 to emit a message such as “cal mode” to indicate tothe user that the system 100 is being calibrated to the effects ofminerals in the soil. The user then maneuvers the search device 105 inan appropriate manner while this calibration is taking place. Forexample, the user lowers the search device 105 slowly to the groundsurface and then returns it to the predetermined height in a smooth,continuous motion for about four seconds. Or, the user moves the searchdevice 105 up and down relative to the ground surface for apredetermined time period. When the user finishes maneuvering the searchdevice 105, the user releases the metal detection control switch 420 andlistens for an audio signal emitted from the device 135 or 137indicating that calibration is complete. For example, the processor 231may send a “cal mode complete” signal to the audio device 135 or 137after the user releases the control switch 420.

Moreover, the user may perform this procedure (step 1705) at any time ifthe user determines that background audio levels have increased ordecreased during normal operation as long as there is no mineralizedsoil or metal in the region.

Next, the user trains the radar detector electronics 235 (step 1710)over ground that is similar to the area to be searched. Training sets abaseline for the mine detection system 100 to compare future readings.Furthermore, the system 100 is retrained when the ground to be swept isdrastically different from the ground on which the system 100 wastrained. In this case, the system 100 is first shut down completely(step 1635) and then restarted (step 1620). To train, the user pushesand holds the trigger switch 435 (FIG. 6) on the interface controller110. Then, the user performs a normal sweep pattern over the ground infront of the user, advancing about ⅓ of the diameter of the searchdevice 105 after each swing while keeping the search device 105 below apredetermined height (for example, 2 inches) from the ground. The usercan then cover about 3-6 feet of ground in a forward direction duringthe normal sweep pattern. The user performs the normal sweep patternwhile the processor 236 sends a signal to the audio device 135 or 137 toemit a “training” sound. The user releases the trigger switch 435 whenthe user hears the sound “training complete” from the audio device 135or 137. The training takes about 45 seconds and at the end of thetraining, the processor 236 sends a signal to the audio device 135 or137 to emit a sound (for example, “localize”) indicating that the usercan begin normal operation of the system 100.

Generally, during start up (step 1620), the user can set the radarsensitivity switch 425 to an up position. The user can adjust the radarsensitivity by moving the switch 425 to accommodate for the user'ssweeping technique or a particular terrain.

After training (step 1710), the user then verifies that the system 100is ready to be operated (step 1715). During verification, the userreleases the trigger switch 435, places the test piece 1510 on theground, passes the search device 105 over the test piece 1510, andverifies proper operation of the metal detector and the radar detectorby listening for audio signals from the devices 135 or 137. If either orboth of the audio signals are not heard, then the user must shut downthe system 100 (step 1635) and repeat startup (step 1620) andpreparation (step 1625).

After the system has been prepared (step 1625), the user can operate thesystem 100 during normal operation (step 1630). During normal operation,the user pushes the trigger switch 435 (FIG. 6) on the interfacecontroller 110 and performs a sweep technique, which is detailed below.During this time, the metal detector (made up of the electronics 230 andthe coil 265) and the radar detector (made up of the electronics 235 andthe antennas 270, 275, and 280) operate independently and simultaneouslyto detect mines in the vicinity of the sweep. Both detectors transmitand receive data and automatically and continuously update the audiosignal sent to the device 135 or 137 to notify the user of any changesin detection that might indicate the presence of a mine. As discussedabove, the two detectors are operationally compatible with each othersuch that they do not interfere with each other during simultaneousoperation.

Referring to FIG. 18 and again to FIGS. 2 and 13, the metal detectorelectronics 230 perform a procedure 1800 during a sweeping operation(either during preparation at step 1625 or during normal operation atstep 1630). Initially, the pulse generator 232 sends pulses to thetransmitter 233 (step 1805), which transmits electric current to thecoil 265 (step 1810). The electric current through the coil 265 inducesa magnetic field 1300 that emanates from the coil 265 and into theground 1305. When the magnetic field strikes a metal object 1310, itinduces a secondary magnetic field in the metal object 1310. Thesecondary magnetic field of the metal object 1310 induces a secondarycurrent in the coil 265. The processor 231 monitors the current from thecoil 265 and detects the secondary current by detecting a change in theelectric current through the coil 265 from the transmitter 233 (step1815). If the processor 231 determines that the secondary current isgreater than a predetermined threshold (step 1820), then the processorsends an audio signal to the device 135 or 137 to indicate to the userthat metal is present under the ground 1305 (step 1825).

Referring to FIG. 19 and again to FIG. 14, the radar detectorelectronics 235 perform a procedure 1900 during a sweeping operation(either during preparation at step 1625 or during normal operation atstep 1630). The radio frequency generator 237 continuously sends a radiofrequency (RF) signal of sufficient strength or power for the radarsensitivity desired (as determined by the configuration of the radarsensitivity switch 425) to the transmitting antenna 270 (step 1905). Thetransmitting antenna 270 emits the RF signal 1400 into the ground 1405(step 1910). Either or both of the receiving antennas 275 and 280collect any RF signals 1410 that have been reflected by an undergroundfeature 1415 and that reach the antenna 275 or 280 (step 1915). Duringthis process, the generator 237 steps the RF signal between a startfrequency and a stop frequency in equal increments. For each frequencystep, the RF signals reflected from the underground feature 1415 arereceived by the antenna 275 or 280, which transmits the RF signals tothe processor 236 (step 1920), which then digitizes and stores thesignals (step 1925). The processor 236 collects the data for all stepsbetween the start and stop frequencies and the data collection isreferred to as a “frequency packet.” The processor 236 analyzes thefrequency packet (step 1930) to determine if a mine is underground (step1940). If the processor 236 determines that a mine is underground, theprocessor 236 sends a signal to the audio device 135 or 137 indicatingthe presence of the mine (step 1945). If the processor 236 determinesthat a mine is not underground (step 1940), then the processor 236simply awaits the next transmission from the antenna 275 or 280 (step1920).

As mentioned above, the user “sweeps” the mine detection system 100 todetect mines, with the quality of the mine detection results beingdirectly related to the quality of the user's sweep technique. Theimportant components to a proper sweep technique are the user's stance,the position of the search device 105, the speed at which the usersweeps the search device 105, and the coverage of the sweep (called alane).

First, the user stands in a comfortable and balanced position thatpermits the user to cover a full lane width without having to changeposition.

Second, referring to FIG. 20, the search device 105 is positionedparallel to and as close to the ground 2000 as possible but not morethan a predetermined height 2005 above the ground. In oneimplementation, the predetermined height 2005 is 2 inches. Moreover,before beginning a sweep, the user adjusts the relative angle betweenthe search device 105 and the shaft 120 to ensure that the search device105 is parallel to the ground during a sweep.

Third, the user sweeps the search device 105 across the ground within apredetermined sweep speed. In one implementation, the sweep speed isbetween about 1 to 3.6 feet/second across a five-foot lane.

Fourth, the user moves the search device 105 across a lane in asstraight a line as possible, while trying not to pull the search device105 back toward the user's body or rock the device 105 near the edge ofthe lane. Referring also to FIG. 21, the actual search width 2100 of theradar detector does not extend to the edges of the search device 105. Inpractice, the search width for the radar detector extends to thelocations of the antennas 270, 275, and 280 and is indicated on a top ofthe search device 105 by a different colored marking, called a sweetspot 282 (FIGS. 1 and 11). The search width 2105 of the metal detectoris approximately equal to the diameter of the coil 265. Because thesearch width 2100 for the radar detector is about ⅓ of the diameter ofthe search device 105, the search device 105 should be moved forward nomore than about ⅓ of the diameter of the search device 105 betweensweeps.

If the user passes the search device 105 over a suspected buried mine ordebris, the processor 231 of the metal detector sends a tone to theaudio device 135 or 137 or the processor 236 of the radar detector sendsa beep to the audio device 135 or 137. In this way, the user candistinguish between the results from the radar detector and the resultsfrom the metal detector. After the user hears the tone or the beep, theuser then investigates the suspected mine further according to aprocedure 2200 as shown in FIG. 22. To investigate the suspected mine,the user typically first tries to repeat the alert signal (that is, thebeep or the tone) (step 2205). To do this, the user repeats the sweepseveral times at different angles over the same area while adjustingsensitivity higher or lower if necessary. If the new sweep does notrepeat the alert signal then the user can continue sweeping the lane.Next, once the alert signal has been repeated, the user can then proceedto determine the object's size and position (step 2210). Meanwhile, theuser also investigates surrounding clues (step 2215) to make an overalldetermination of the location of a mine.

Referring also to FIGS. 23A and 23B, in determining the object's sizeand position at step 2210, the user performs a procedure 2210 if usingthe metal detector to investigate. First, the user releases the triggerswitch 435 and waits for an audio ready signal such as “localize” (step2300). If needed, the user then moves the audio control switch 430 tothe right to activate the metal detector only (step 2305). Next, theuser moves the search device 105 back from the suspected mine area 2350until the audio sound for the metal detector diminishes (step 2310) andthen moves the search device 105 toward the center 2355 of the suspectedmine area 2350 until the audio sound for the metal detector is heard orincreases (step 2315). The user moves the search device 105 back andforth and in and out such that the search device 105 spirals around thetarget area (step 2320), thus forming a spiral pattern 2360.

Referring also to FIGS. 24A and 24B, in determining the object's sizeand position at step 2210, the user performs a procedure 2211 if usingthe radar detector to investigate. First, the user releases the triggerswitch 435 and waits for an audio ready signal such as “localize” (step2400). Then, the user establishes the suspected mine pattern using theprocedure 2210 detailed in FIG. 23B (step 2405). If needed, the userthen moves the audio control switch 430 to the left to activate theradar detector only (step 2415). Next, the user moves the search device105 back from the suspected mine area 2450 until the audio sound for theradar detector stops (step 2420). Then, the user moves the search device105 in short sweeps within the suspected mine area 2450 and around theapproximate center of the mine 2355 until the audio sound for the radardetector is heard (step 2425). The user continues the short forwardsweeps through the suspected mine area 2450 while the radar detectoralerts are activating, thus forming a zigzag pattern 2460. The user thenrepeats the zigzag pattern from several different approach angles (onealternate zigzag pattern 2465 is shown in FIG. 24C) to verify theresults of the suspected mine location (step 2430).

The user can also use characteristics of known mines to evaluate theresults of the investigation. For example, an anti-tank, metallic mine(AT-M) shows a metal detector footprint of a semi-circular halo of about20-26 inches from the mine center when buried at a depth of 5 inches anda radar detector footprint of an outside edge of about 13 inches indiameter.

Other implementations are within the scope of the following claims. Forexample, the audio signals sent to the audio device 135 or 137 may besounds other than beeps or tones.

Referring also to FIGS. 25A and 25B, in another implementation, insteadof the telescoping shaft 120, the shaft 2520 is articulated at joints2500 to form segments 2505. Thus, each segment 2505 can be folded overto reduce the length for storage and transportation (as shown in FIG.25B).

The mine detection system 100 may include infrared detection integratedwith the radar and the metal detection. The radar detector may includemore than one transmitting antenna and more than two receiving antennas.

In the procedure discussed above, the metal detector (made up of theelectronics 230 and the coil 265) and the radar detector (made up of theelectronics 235 and the antennas 270, 275, and 280) operateindependently and simultaneously to detect mines in the vicinity of thesweep. Thus, each detector includes its own processor. However, inanother implementation, a single processor can be used to control boththe metal detector and the radar detector. The processor can run asingle algorithm for analyzing the results and notifying the user of anychanges in detection that might indicate the presence of a mine.

In one implementation, the processor 236 analyzes the data (that are inthe form of packets) from the transmitting and receiving components ofboth the radar detector and the metal detector to determine if a mine isunderground at step 1940. Referring to FIG. 26, in this implementation,the processor 236 uses a procedure 2600 that begins by receiving thedata packet from the radar detector receiving component (for example,the antennas 275 and 280) (step 2605) and receiving the data packet fromthe metal detector that came from its receiving component, that is, thecoil 265 (step 2610).

The processor 236 analyzes a model of radar detector response to currentground conditions using a principal component analysis to describeclutter features, as detailed below (step 2615). The processor 236 alsotransforms the radar data from the frequency domain to the time domainin order to analyze the depth of the anomaly (step 2620). The processor236 receives results from the analysis of the metal detector (step 2625)and uses these results later to eliminate clutter noise and localizealarms from the radar detector.

Next, the processor 236 compares the results of the model analysis fromstep 2615, the depth analysis from step 2620, and the metal detectoranalysis from step 2625 (step 2630) to make a determination of whetheran alert signal should be sent to the audio device 135 or 137 (step2635) based on a signal threshold 2640 that depends, at least in part,on the sensitivity setting 2645 from the radar sensitivity switch 425.

Additionally, at various stages (for example, steps 2650, 2655, and2660) during the procedure 2600, the processor 236 adjusts the signalthreshold 2640 to maintain a constant false alarm rate (CFAR). Often,the alarm rate can rapidly rise or drop with abrupt changes inbackground statistics due to changing ground conditions. Thus, theprocessor 236 dampens the effects of the changing ground conditions byrecognizing a rapid change in background statistics and adjusting thesignal threshold 2640 on the fly to accommodate for such changes.

Referring also to FIG. 27, the model of radar detector response istrained prior to use of the mine detection system 100 using a procedure2700. Initially, data is collected from a trial run in a mine-freeregion such that the only features present during the trial run areclutter features. Typically, clutter and noise data remain relativelyconstant from scan to scan and often contain less energy than dataobtained from scans of mines. Ultimately, common features among theclutter scans are captured and new scans that display significantlydistinct features are considered to contain mines.

Although the scans for data can be applied to many different types ofclutter features, the scans for data are based on principal componentsanalysis (PCA), which describes features through principal components,thus permitting automation and enabling adaptation to clutter featuresin local environments. The number of variables involved in the modellingis reduced and the structure of the relationships between variables canbe detected using PCA.

Basically, PCA involves a mathematical procedure that transforms anumber of possibly correlated variables into a smaller number ofuncorrelated variables that are called principal components. The firstprincipal component accounts for as much of the variability in the dataas possible, and each succeeding component accounts for as much of theremaining variability as possible. PCA determines a direction with themost variance and rotates the space such that this direction is now thefirst dimension. Then, PCA finds the direction with the next largestvariance and rotates the space such that this direction is the seconddimension. This process continues until all dimensions are accountedfor. The result is a new feature space with the same number ofdimensions as the original space but with the variance concentrated inthe lower order dimensions.

In general, the mathematical technique used in PCA is eigen analysis inwhich the eigenvalues and the eigenvectors of a square symmetric matrixare solved with sums of squares and cross products. The eigenvectorassociated with the largest eigenvalue has the same direction as thefirst principal component. The eigenvector associated with the secondlargest eigenvalue determines the direction of the second principalcomponent. The sum of the eigenvalues equals the trace of the squarematrix and the maximum number of eigenvectors equals the number of rows(or columns) of this matrix.

Referring to FIG. 27, to begin the PCA process, the processor 236receives the collected data from the trial run in the form of frequencypackets (step 2705). Typically, several hundred clutter-only frequencypackets are received. Next, the data is prepared (step 2710) and thecovariance matrix is determined (step 2715). Then, using single valuedecomposition, the eigenvalues and eigenvectors are obtained (step2720).

Referring again to FIG. 26, once the model is trained using theprocecedure 2700, the processor 236 can update the model using aprocedure 2615. Initially, the data received in the form of frequencypackets (step 2605) are prepared (step 2665). Then, the processor 236processes the prepared data using PCA (step 2670), a procedure furtherdiscussed below. Based on the PCA, the processor 236 outputs apreliminary result of whether a mine is present (step 2675).

Referring also to FIG. 28, the processor 236 processes the prepared datausing a PCA procedure 2670. Initially, the processor 236 projects theprepared data into eigenspace by multiplying the data vector by theeigenvalue matrix (step 2800). Then, the results are provided in theform of a function of the projection of the data and the weight matrix(step 2805).

Because PCA can safely discard some of the higher order dimensions,noisy sources of variability are removed and the dimensionality of theinput is reduced, thus making modelling simpler. Referring to FIG. 29,sample results for PCA in the form of a graph 2900 are shown for variousmine locations 2905. Raw data 2910 is input into PCA and PCA outputs asignal 2915 that has a strength measured in the upper graph 2920. Asshown, PCA enhances the target-to-clutter signal ratio.

Referring again to FIG. 26, the processor 236 transforms the radar datafrom the frequency domain to the time domain at step 2620. As discussedabove, during operation of the system 100, the radar data is steppedthrough frequencies. Typically, the range through which the radar isstepped is about one and a half gigahertz. The processor 236 usesFourier transformation to transform the radar data from the frequencydomain to the time domain. Because the data is transformed into the timedomain, information about depth (if using two or more antennas) ordistance to the mine may be obtained.

The system 100 employs two receiving antennas 275 and 280 to determinethe depth of a mine. For example, with a single receiving antenna, anobject located five inches directly below the antenna might appear to bein the same time domain location as an object located three inches deepbut four inches laterally from the antenna (where the distance from theantenna to the object is still five inches). By using a second receivingantenna, data from the two receiving antennas may be correlated topermit a higher degree of accuracy and to permit a determination ofdepth.

Referring again to FIG. 26, the processor 236 compares the results ofthe model analysis, the depth analysis, and the metal detector analysis(step 2630) to make a determination of whether an alert signal should besent to the audio device 135 or 137 (step 2635). The comparison maydetermine that the alert signal should be sent even if model analysisprovides a weak mine signal if the metal detector analysis signal isstrong.

Alternative detection features may be incorporated into a multi-modelandmine detector (MLD). Examples of such alternative detection featuresinclude perimeter warning and through wall sensing using Dopplerprocessing for motion detection, along with buried and in-wall cachedetection using a variant of the mine detection algorithm and theexisting metal detector 1350 and radar detector 1450. Variouscombinations of separate functions, such as dual mode or even five ormore separate functions, may be loaded onto the MLD at the factory toprovide the user with the ability to select which of the functions ormodes to exercise at any time.

A MLD may be identical to the systems described above in userfunctionality, while also including switches, such as in the controlsection 400, internal to the device that are brought into play by theuser mode selection. The MLD may provide visual or audio warnings oftarget identification with the control section 400 shown in FIGS. 5 and6, or as shown in FIGS. 31 and 32, an optional clip-on display 3000 andinterface with the control section may be provided for the MLD to permitthe operator to view images of target detection results. For example,perimeter warning or through wall sensing may be accomplished viaDoppler processing of the radar return, but with the system antenna orsensor head pointing outwards (rather than straight down into the groundwhen in mine detection mode). The system may be laid on the ground or ina fixture to keep the system still. The long range capability of thismode is over 100 feet.

FIG. 30 is a flow chart of an alternative processing procedure that maybe performed by the processor of the radar detector within the minedetection system of FIG. 1. As seen in FIG. 30, the data processingsteps include a prefiltering step 3005, a simple range and velocitytracking step 3010, an angle calculation 3015 and a plan view displaygeneration step 3020 on a display 3000. In one implementation, thethrough wall and perimeter (or intrusion) warning modes use Doppler ATRprocessing. An automatic target recognizer (ATR) is an algorithm thatlocates potential targets in an image and identifies the types oftargets. An ATR algorithm typically includes several processing stages.In the first stage, a target detector, operating on the entire image,detects some potential target areas (target chips). In order to reducethe false-alarm rate, the second stage attempts to reject falsetarget-like objects (clutter) and retain targets. In the third stage, aset of features is first computed and then each target image isclassified into one of a number of classes. Most ATR algorithms thathave been developed operate on a single frame of still imagery todetect, recognize, and geolocate targets of interest. The introductionof digital motion imagery has facilitated ATR processing of motionimagery that is particularly advantageous for the through wall andperimeter warning operating modes.

FIG. 31 is a representative view of a display 3000 during a through walldetection mode that uses Doppler ATR processing when a search device isflush against a wall. FIG. 32 is a representative view of a displayduring a through wall detection mode that uses Doppler ATR processingwhen a search device is positioned away from a wall. Through wall, likeperimeter (or intrusion) warning, is also accomplished using Dopplerprocessing. However, through wall processing first includes use of themetal detector to select metal-free wall areas for the radar to passthrough. In the through wall mode, the user can then turn off the metaldetector so as not to interfere with the audio return of the Dopplerprocessing. FIGS. 31 and 32 show examples of through wall detection ofwalking persons, first with the sensor head flush against the wall andthen at a two foot standoff. Test results of perimeter warning andthrough wall sensing using Doppler ATR processing produced favorableresults, e.g., detection capability of 100 feet or more, when the searchdevice 105 was positioned against or offset (approximately two feet asshown in FIG. 32) from a wall made of drywall, concrete block,reinforced concrete and brick.

Buried cache and in-wall cache detection is accomplished using similarscanning and system training techniques that have been successfully usedfor the buried land mine detection described in greater detail abovewith respect to FIGS. 1-29. The scanning method is similar to thatdescribed for buried land mine detection with the exception that thesearch device 105 is moved relative to surfaces that are not necessarilyhorizontal with respect to the operator, e.g., the vertical andhorizontal walls of a cave. The radar system technology used for thismulti-mode landmine detector can also be separated into discrete,application specific devices or systems, depending on user preference.In fact, any combination of one, two, three or four modes can bedesigned into the hardware or software for separate products.

FIG. 33 is a schematic view showing a selection device 3300 for a minedetection system having multiple operating modes. The selection devicepermits an operator to select between a variety of operating modes. Forexample, five operating modes are shown but any combination of operatingmodes may be preloaded into the mine detection system at the factory.Selecting an operating mode causes the system to designate apredetermined process for analyzing data during the selected mode.Accordingly, the processor(s) operatively connected to the radardetector and the metal detector will employ slightly differentprocessing schemes, such as Doppler processing, during the through walldetection and perimeter warning modes. The selection of either of thesetwo modes will therefore initiate a process for analyzing data that isdifferent than those processes (FIG. 26) used for the buried mine,buried cache and in-wall cache detection modes.

Other implementations are within the scope of the following claims.

1. A multi-mode target detection system comprising: a ground penetratingmetal detector; a ground penetrating radar detector; and a controlsection having a selection device for selecting at least two operatingmodes from the group consisting of a buried land mine detection mode, athrough wall detection mode, a perimeter warning mode, a buried cachedetection mode and an in-wall cache detection mode.
 2. The system ofclaim 1, wherein the ground penetrating metal detector comprises: atransmitter, a coil coupled to the transmitter to produce a magneticfield; and a signal processor coupled to the coil and configured todetect a secondary magnetic field.
 3. The system of claim 1, wherein theground penetrating radar detector comprises: a radio frequencygenerator; and a radio frequency transmitter coupled to the radiofrequency generator to transmit radio-wave signals toward the ground. 4.The system of claim 3, wherein the ground penetrating radio detectorcomprises: a radio frequency receiver that receives radio-wave signalsfrom the ground, and a signal processor coupled to the radio frequencyreceiver to detect the radio-wave signals, wherein the radio frequencyreceiver includes an antenna.
 5. The system of claim 1, whereinoperating modes supported by the control section include all of theburied land mine detection mode, the through wall detection mode, theperimeter warning mode, the buried cache detection mode and the in-wallcache detection mode.
 6. The system of claim 1, wherein the metaldetector includes a coil that produces a magnetic field and the radardetector includes a transmitting antenna that transmits radio-wavesignals toward the ground and a receiving antenna that receivesradio-wave signals reflected from objects within the ground.
 7. Thesystem of claim 6, wherein the antennas are surrounded by the coil andthe antennas are shielded from external electromagnetic radiation. 8.The system of claim 1, further comprising an output device that outputsa signal indicating a presence of an object if either the groundpenetrating metal detector, the ground penetrating radar detector, orboth detect the presence of the object.
 9. The system of claim 1,wherein the ground penetrating radar detector and the ground penetratingmetal detector are housed in a single housing and operation of the metaldetector does not interfere with operation of the radar detector. 10.The system of claim 1, further comprising an output device forindicating a detection of a target in said at least two operating modes.11. The system of claim 10, wherein the output device includes a visualdisplay.
 12. The system of claim 10, wherein the output device includesan audio or visual alarm.
 13. A target detection system comprising: anintegrated search device housing a radio-wave transmitter and a metaldetector coil; a first set of electronic components coupled to the radiotransmitter; a second set of electronic components coupled to the metaldetector coil; and a processor for detecting a target through at leasttwo modes selected from the group consisting of a buried land minedetection mode, a through wall detection mode, a perimeter warning mode,a buried cache detection mode and an in-wall cache detection mode. 14.The system of claim 13 further comprising a radio-wave receiver, whereinthe radio-wave transmitter and receiver are shielded from externalelectromagnetic radiation.
 15. The system of claim 13, wherein operatingmodes supported by the control section include all of the buried landmine detection mode, the through wall detection mode, the perimeterwarning mode, the buried cache detection mode and the in-wall cachedetection mode.
 16. The system of claim 13 further comprising an outputdevice for indicating a detection of a target in said at least twooperating modes.
 17. The system of claim 16, wherein the output deviceincludes a visual display.
 18. The system of claim 16, wherein theoutput device includes an audio or visual alarm.
 19. A method ofdetecting targets in a multi-mode target detection system, the methodcomprising: selecting an operating mode for detecting a target, whereinthe operating mode is selected from the group consisting of a buriedland mine detection mode, a through wall detection mode, a perimeterwarning mode, a buried cache detection mode and an in-wall cachedetection mode; transmitting radio-wave frequency energy into asurrounding region; detecting radio-wave frequency energy reflected byan object in the surrounding region; and analyzing data obtained fromtransmitting and detecting radio-wave frequency to detect the target inthe selected operating mode.
 20. The method according to claim 19,wherein selecting the operating mode comprises initiating apredetermined data processing step for the selected operating mode. 21.A method of detecting targets comprising: providing a detection systemhaving a metal detector and a radar detector for collecting andanalyzing data taken from a surrounding region; selecting an operatingmode for detecting a target, wherein the operating mode is selected fromthe group consisting of a buried land mine detection mode, a throughwall detection mode, a perimeter warning mode, a buried cache detectionmode and an in-wall cache detection mode; and detecting the target withthe detection system.
 22. The method of claim 21, wherein detecting thetarget with the detection system further comprises: analyzing data takenfrom the surrounding region using the metal detector, and analyzing datataken from the surrounding region using the radar detector.
 23. Themethod of claim 21 further comprising training the detection systemusing a principal components analysis of the background clutter data.24. The method of claim 21, wherein detecting the target with thedetection system includes doppler processing of data from the radardetector.
 25. The method of claim 24, wherein doppler processing of datafrom the radar detector is performed during the through wall detectionmode and the perimeter warning mode.
 26. The method of claim 21, whereindetecting the target with the detection system during the through walldetection mode further comprises analyzing data taken from thesurrounding region using the metal detector.
 27. The method of claim 21further comprising automatically adapting the detection system to thesurrounding region to determine whether a mine is present in thesurrounding region.
 28. The method of claim 21, wherein adapting thedetection system includes using a principal components analysis of thedata taken from the surrounding region.
 29. The method of claim 21further comprising: analyzing data taken from the surrounding regionusing a metal detector, analyzing data taken from the surrounding regionusing a radar detector based on the training, and analyzing a depth ofan object detected by the radar detector using the data.
 30. The methodof claim 29, wherein analyzing the depth of the object includestransforming data from the radar detector from the frequency domain tothe time domain.
 31. The method of claim 29, wherein analyzing the depthincludes receiving data from two or more antennas of the radar detector.32. The method of claim 29, wherein analyzing data taken from thesurrounding region using the radar detector includes using a principalcomponent analysis of the data.